His comment on the sidelines of an event hosted by the global airline trade group marks one of the industry's first acknowledgements that the mosquito-borne virus could hit revenue.

"A number of members have expressed concern that they may already be seeing some effect on travel, particularly in the Americas," he said. "When we publish (traffic) numbers, particularly I think the regional numbers for January, perhaps there will be the first indication of that."

Tyler could not comment on what kind of impact the airlines were seeing, whether destination switches by travellers or lower bookings overall.

Bookings to Zika-hit parts of the Americas fell 3.4 percent from a year ago between Jan. 15, when the U.S. Centers for Disease Control and Prevention issued a travel advisory for pregnant women, and Feb. 10, according to a report last week by travel data analysis company ForwardKeys.

Scientists are investigating a potential link between Zika infections of pregnant women and more than 4,300 suspected cases in Brazil of microcephaly, a condition marked by abnormally small head size that can result in developmental problems.

Other travel companies, such as cruise ship operators Carnival Corp (>> Carnival Corp) and Norwegian Cruise Line Holdings Ltd (>> Norwegian Cruise Line Holdings Ltd), have yet to report a hit from the virus.

Top airlines have said identifying any bookings shift from Zika would be difficult because unit revenue already is down to places such as Brazil because of the country's economic crisis.

Some air ticket prices are falling nonetheless. The lowest fares to debt-strapped San Juan, Puerto Rico have fallen 22 percent on average from a year ago, according to an early February analysis of six of the busiest U.S. domestic routes to the island's capital by Harrell Associates.

Puerto Rico is one of 28 countries and territories in the Americas battling Zika. At least three conferences at major Puerto Rican hotels were recently cancelled and one postponed because of concerns over the virus.

Much remains unknown about Zika, including whether the virus actually causes microcephaly in babies. Brazil said it has confirmed more than 580 cases of microcephaly, and considers most of them to be related to Zika infections in the mothers. Brazil is investigating an additional 4,100 suspected cases of microcephaly.

(Reporting by Jeffrey Dastin in New York; additional reporting by Abhijith G in Bengaluru; Editing by David Gregorio; Editing by Chizu Nomiyama)

By Jeffrey Dastin